As semiconductors become smaller and the devices using semiconductors become more sophisticated and therefore more demanding of the semiconductors, the perfectness property of semiconductors becomes an issue of great concern. The manufacture of semiconductors involves the use of reactive gases that are composed of various elements. In addition, manufacturing processes such as metal-organic chemical vapor deposition (MOCVD) and other related manufacturing techniques are used in the manufacture of semiconductors. In these processes the purity of the reactive gases plays a large part in determining the quality of the semiconductor product being manufactured, and in particular the electronic quality of the semiconductor product. Consequently, there is an increasing demand in the microelectronics industry for ultra-pure process gases. Thus, the ultra-purification of gases useful in microelectronics processes has experienced extensive technological effort and advances.
Existing methods of purifying gases used in manufacturing microelectronics devices are generally insufficient for meeting the need for ultra-pure gas. While parts-per-billion (ppb) levels of impurities were tolerable at one time, such levels are now regarded in many processes as too high. This technological effort is nourished by improvements in the analytical techniques that are used to detect impurities in gases. Presently, the ability exists to provide impurity detection limits that are in the ppt levels, for example by using Atmospheric Pressure Ion Mass Spectrometry (APIMS).
Group IIIB metals (e.g., gallium (Ga) and indium (In)) and group VB elements (e.g., phosphorus (P), arsenic (As), and nitrogen (N)) are of special importance in the manufacture of semiconductors in that they are constituents of the so-called Group III/V semiconductors. For example, arsine (AsH3), phosphine (PH3) and ammonia (NH3) are used in the manufacture of Group III/V semiconductors such as gallium arsenide (GaAs), indium phosphide (InP) and gallium nitride (GaN), respectively. Traces of foreign elements in these semiconductor materials are harmful, especially if the foreign elements are Group IVB elements (e.g., Si and Ge) and/or Group VIB elements (e.g., S and Se), which adversely contribute an acceptor effect or a donor effect to the semiconductor material. Unfortunately, trace impurities of Group IVB and VIB elements are very common in so called “pure gases.” For example, phosphine and arsine may include traces of silane (SiH4), germane (GeH4), hydrogen sulfide (H2S) and hydrogen selenide (H2Se). In addition, trace quantities of oxygen (O2), oxides such as carbon monoxide (CO) and/or carbon dioxide (CO2), and oxides derived from phosphine and arsine (e.g., HxPyOz, and HxAsyOz, wherein x, y and z are small integer numbers) have also been detected in “pure gases.” Such impurities are also harmful in semiconductor processes.
Impurities in hydride gases used in the production of semiconductor devices, especially hydride-impurities of other elements, may originate from the hydride bulk gas itself, or from materials that are within gas handling and distribution devices such as gas containers, gas cylinders, gas valves and gas regulators, and even from gas lines that interconnect these devices.
A need remains in the art for an effective purifier apparatus and purification method for removing trace impurities from so-called pure gases, specifically the removal of trace hydride impurities from bulk or matrix hydride, non-reactive and inert gases. In particular, there is a need for the selective removal of trace quantities of hydride impurities of Group VB elements such as phosphorus (P) and arsenic (As) and hydrides of Group IVB elements such as silicon (Si) and germanium (Ge) from hydride gases and non-reactive or inert gases. Such hydride impurities pose environmental and health hazards because of their extreme toxicity, and elimination of these hydrides from bulk and matrix gases down to the sub-ppm level is desirable.